1. Field of the Invention
The present invention relates to an eye gaze detection apparatus and an eye gaze detection method.
2. Description of the Related Art
An eye gaze detection apparatus has been proposed for detecting a gaze position of an operator or a subject on a viewing surface such as a monitor screen. For example, a method to achieve a non-contact eye gaze detection that reliably detects an eye gaze direction without attaching any device to a face of the subject has been known. With this method, an on-eyeball reflection of light emitted from a light source is detected to calculate a pupil center and a corneal curvature center, and then a line that connects the pupil center and the corneal curvature center is detected as an eye gaze.
According to a method stated in Japanese Patent No. 2739331, two cameras and two light sources are used to detect two corneal reflection points within an eyeball. The corneal curvature center is calculated from these two corneal reflection points, and the eye gaze is detected based on a positional relationship between this corneal curvature center and a pupil center. According to a method stated in Japanese Patent No. 4824420, by using one camera and two light sources, the corneal curvature center is calculated from a line of intersection of planes, each plane containing two corneal reflection points. The eye gaze is detected based on the positional relationship between the corneal curvature center and the pupil center.
The methods stated in the above-described documents, however, have had a problem that the apparatus to detect an eye gaze with high accuracy becomes complicated in configuration and large in size. For example, when using two light sources, two reflection points corresponding to the respective light sources are detected separately, and thus, the two light sources need to have a predetermined minimum distance therebetween. This is because if the distance between the two light sources is too short, the two reflection points might overlap, making it difficult to separate them from each other.
Therefore, there is a need for an eye gaze detection apparatus and an eye gaze detection method to be capable of achieving improved detection accuracy.